Me 410 Exhaust Flames

[Chris Goss]

Looking through RAF combat reports, in each night interception Me 410s were easily identified by "electric blue" or pale yellow exhaust flames. This has puzzled me-why the two colours and surely exhaust dampers were used so why were they so so ineffective?

[MW Giles]

The colour is simple chemistry - same as on a bunsen burner

Blue - lean mixture - complete combustion of fuel
Yellow - rich mixture - incomplete combustion

Flame dampers never give complete damping as there is a trade off between damping of the exhaust and drag, length of damper, back pressure on engine reducing performance, loss of thrust from exhaust gases etc

They could also degrade over time - hours stuck in a howling gale subjected to high temperatures.

Accounts of night fighters indicate that from directly behind you could often find the exhaust glow

[Chris Goss]

Thanks-makes sense but in all combat reports I have read so far, these flames are more than evident whatever the colour

[schwarze-man]

Hi Chris,
Yes, the exhaust-gas plume is visible on large piston aero-engines at night. Certainly, stubs are notorious for giving off a lot of light, just look at night-flying Hurricanes with those large flat plate shades to stop blinding the pilot.
The light is certainly reduced by flame dampers, although many are not very good. I think the Bf 110 night fighters with the very large flame dampers are a good illustration of an effective system. The exhaust gas needs time, distance and dilution to cool and loose the glow. Here, the glowing gas is contained in tubes that prevent it being seen to the sides and forward. Cooling air is allowed in at the front and again, about half way down the damper pipe. This is probably one of the effective dampers but, the pipe is still long despite the dilution and baffling inside.
Another factor is that the flames do vary considerably with power changes.
Overall, flame-dampers did vary in effectiveness. I am not certain that Me 410 night fighters or intruders were all fitted with flame dampers, and their large 44litre DB 603 engines would certainly give a large exhaust flame, so possibly the Me 410 was weak in this respect.

Cheers

SM

[Chris Goss]

Thanks SM-it would appear that this was a problem for the 410